The spell-checking will be enabled at the portable version of Balabolka, if any spell checker is installed on the user's computer.
If you want to have Hunspell dictionaries on your USB drive, you need to do this:

Download the portable variant of Hunspell for a language from the list below.

Unzip the archive to the subfolder 'Hunspell' in the folder 'Balabolka' on the USB drive.

After that the portable version of Balabolka will load the Hunspell files from the portable drive, not from the user's computer.